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06-26-2012 07:02 AM - edited 10-01-2014 04:37 AM

I always have the same question: how to prescribe correctly the Damping effects in a FE model to be solved with the Advanced Nonlinear Dynamics Transient analysis (SOL601, 129) module using implict direct integration?.

In Nonlinear Static/Transient Analysis we have the following types of dampings:

• Also wen selecting "

• And finally I understand we have the DAMPER ELEMENTS like PBUSH elements to mesh damping explicitely on elements.

But what I am looking for is a correlation between the modal damping we use for instance in LINEAR modal time history analysis of say 2% and the equivalent damping to prescribe DIRECTLY in a nonlinear transient implicit dynamic analysis using Rayleigh parameters alfa & beta constants, any HELP is welcome -- thanks!.

Por instance, solving the CANTILEVER BEAM example posed yesterday as NonLinear Transient Dynamic (SOL601,129) I get the following answer for displacements of T2 Translation and T2 Accelerations vs. time for tip node #21 and also the T2 Constraint Force at node#1:

Comparing results we can see that the nonlinear transient dynamic response (SOL601,129) WITHOUT PRESCRIBING ANY RAYLEIGH DAMPING values are the most demanding values, then the need to prescribe correctly the damping constant for nonlinear transient dynamic analysis. Please note this is a simply beam model where not any nonlinearity of large displacements neither material exist, but in real problems this could be critical.

Best regards,

Blas.

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